Light-developable direct-print silver halide emulsions



3,507,657 LIGHT-DEVELOPABLE DIRECT-PRINT SILVER HALIDE EMULSIONS Theodore J. Kitze, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Nov. 10, 1965, Ser. No. 507,233 Int. Cl. G03c 1/02, 1/28 US. C]. 96-94- 12 Claims ABSTRACT OF THE DISCLOSURE Improved light-developable, direct-print silver halide emulsions comprise silver halide grains formed in an acidic medium in the presence of a water-soluble thiocyanate and an organic thioether silver halide solvent. In one aspect, the improved silver halide emulsions provide good photographic response characteristics, such as speed, when used under a wide variety of exposure conditions.

The present invention relates to photography, and more particularly, to light-developable, direct-print photographic silver halide emulsions.

Radiation-sensitive photographic elements adapted for light recording, e.g., oscillographic recording, are known. Typical of such photographic elements are the developingout and print-out type. The developing-out type of photo graphic element, as the name implies, requires that the exposed material be chemically developed and fixed in order to provide a stable visible image. The print-out type of photographic element develops on exposure and requires no development step. The print-out type is generally much slower than the developing-out type and the images are unstable and have a short life.

A third type of radiation-sensitive photographic element especially suitable for light-writing and oscillo graphic recording comprises a hydrophilic colloid-silver halide emulsion layer which, when exposed to a high intensity source of electromagnetic radiation, forms a latent image which can then be developed by subsequent general exposure to a second source of radiation of lower intensity. Such direct-Writing or direct-print emulsions are faster than print-out emulsions and require no chemical development. However, many of the recording photographic elements of this third type have a slow rate of photodevelopment and the background areas tend to build up to obscure the image on subsequent exposure to light at an undesirably high rate.

It is an object of this invention to provide a new class of light-developable, direct print, radiation-sensitive silver halide emulsions.

It is another object of this invention to provide novel photographic silver halide emulsions suitable for preparing direct-print recording photographic elements having a high rate of photodevelopment.

It is another object of this invention to provide new light-developable, direct-print emulsions having relatively high sensitivity or speed.

It is another object of this invention to provide new light-developable, direct-print photographic silver halide emulsions that are characterized as having high density differential between the initially exposed and unexposed areas upon photodevelopment.

It is still another object of this invention to provide new light-developable, direct-print silver halide emulsions that can be chemically developed to form archival-quality records.

It is also an object of this invention to provide new light-developable photographic silver halide emulsions that have high resistance in the initially unexposed areas nitecl States Patent to density increase upon photodevelopment and subsequent exposure to room-light.

These and other objects of the invention are accomplished with light-developable, direct-print silver halide emulsions containing silver halide grains grown or formed in an acid media in the presence of a water-soluble thiocyanate and an organic thioether silver halide solvent.

Particularly useful water-soluble thiocyanates utilized during the grain formation of the silver halide of the emulsions of the invention are alkali metal thiocyanates such as sodium thiocyanate and potassium thiocyanate.

The amount of water-soluble thiocyanate utilized can be widely varied depending on the effect desired, the nature of the water-soluble thiocyanate and related variables. Concentrations of about .1 to 50 grams of the thiocyanate per mole of silver halide are suitably utilized, with about 1 to 10 grams of the thiocyanate per mole of silver halide being more generally utilized.

Suitable organic thioether silver halide solvents that can be utilized during the grain formation of the silver halide emulsions of the invention are described in French Patent 1,368,647, issued June 22, 1964, and in copend ing McBride application Ser. No. 452,009 filed April 29, 1965.

Aqueous solutions of suitable organic thioether silver halide solvents utilized during the grain growth or formation of the silver halide grains of the present emulsions have a greater solubility for silver chloride than water. More specifically, such thioether silver halide solvents are those which, when utilized in aqueous solutions (60 C.) at 0.02 molar concentrations, are capable of dissolving more than twice the amount (by weight) of silver chloride than that which can be dissolved by water at 60 C.

The amount of thioether silver halide solvent utilized can be widely varied depending on the effect desired, the nature of the thioether utilized and related variables. Concentrations of about .1 to 50 grams of thioether per mole of silver halide are suitably utilized, with about 1 to 10 grams of thioether per mole of silver halide being more generally utilized.

Typical organic thioether silver halide solvents that can be suitably utilized in preparing the emulsions of the invention contain at least one moiety wherein oxygen and sulfur atoms are separated by an ethylene radical (e.g., -OCH CH --S). Generally, the subject silver halide solvents have 1 to 3 thioether atoms (S) although silver halide solvents having more than 3 thioether atoms can be utilized.

Certain of the present organic thioether silver halide solvents can be represented by the formulas:

wherein: r and m are integers of 0 to 4; n is an integer of l to 2; k is an integer of 1 to 4; p and q are integers of 0 to 3; X is an oxygen atoms (--O), a sulfur atom (S), a carbamyl radical a carbonyl radical or a carboxy radical i (O OH) R and R are ethylene oxide radicals (OCH CH Q and Z are hydroxy radicals (OH), carboxy radicals, or alkoxy radicals (-Oalkyl) wherein the alkyl group has 1 to carbon atoms; and Q and Z can also be the substituents described for X linked to form a cyclic compound.

Preferred organic thioether silver halide solvents suitable for forming the emulsions of the invention include compounds represented by the formulas:

wherein: r is an integer of 1 to 3; s is an integer of 1 to 2; R is an alkylene radical having 1 to 5 carbon atoms and is preferably ethylene '(-CH CH R is an alkyl radical having 1 to 5 carbon atoms and is preferably ethyl; and R is an alkylene radical having 1 to 5 carbon atoms and is preferably methylene (-CH A wide variety of light-developable, direct-print photographic silver halide emulsions can be utilized in the invention, such being well known to those skilled in the art. Suitable silver halides include silver choride, silver bromide, silver bromoiodide, silver chloroiodide, and silver chlorobromoiodide. The preferred emulsions are those wherein the silver halide contains at least 50% bromide, less than iodide and less than 50% chloride on a molar basis. For a description of suitable emulsions, reference is made to Davey et al., US. Patent 2,592,250, issued Apr. 8, 1952; and Glafkides, Photographic Chemistry, vol. 1, pp. 31-2, Fountain Press, London.

The so-called internal image emulsions are particularly useful in the invention, such having silver halide grains wherein a predominant amount of the sensitivity is internal to the grains. Such internal image-forming emulsions are those which, when measured according to normal photographic techniques by coating a test portion of the emulsion on a transparent support, exposing to a light intensity scale having a fixed time between 1 1O and 1 second, bleaching 5 minutes in a 0.3% potassium ferricyanide solution at 65 F. and developing for about 5 minutes at 65 F. in Developer B below (an internaltype developed), having a sensitivity, measured at a density of 0.1 above fog, greater than the sensitivity of an identical test portion which has been exposed in the same way and developed for 6 minutes at 68 F. in Developer A below (a surface-type developer).

DEVELOPER A G. N-methyl-p-aminophenol sulfate 0.31 Sodium sulfite, desiccated 39.6 Hydroquinone 6.0 Sodium carbonate, desiccated 18.7 Potassium bromide 0.86 Citric acid 0.68

Potassium metabisulfite 1.5 Water to make 1 liter DEVELOPER B G. N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide 5.0 Sodium thiosulfate 10.0

Water to make 1 liter In preparing the present silver halide emulsions, the water-soluble silver salt and the water-soluble halide are reacted to precipitate the silver halide under acidic conditions. The pH of the silver halide precipitation is typically less than 6 and preferably less than 5. Such acids as phosphoric, trifiuoroacetic, hydrobromic, hydrochloric, sulfur and nitric are typically utilized in the silver halide. precipitating media to maintain acidic conditions. An excess of water-soluble halide is more generally used. The pAg during the silver halide precipitation is more generally about 8 to 10.

The water-soluble thiocyanate and the thioether silver halide solvent can be added to the silver halide emulsion at any stage of the preparation thereof before the silver halide grains have attained their ultimate size and shape, such as to the colloidal material in which the silver halide is precipitated, in combination with one of the watersoluble salts utlized to form the silver halide such as with the water-soluble silver salt (e.g., silver nitrate) or with a water-soluble halide such as an alkali metal halide, to the silver halide prior to or during the ripening of the silver halide, or during one or more of such emulsion preparation steps.

The present silver halide emulsions can be washed after precipitation such as by the methods described in US. Patents 2,614,929 and 2,618,556. The silver halide grains of the emulsions of the invention generally have an average grain size of about .1 to 10 microns, and more generally about .5 to 2 microns, in diameter.

Although silver halide emulsions are generally made with an equivalent or slight excess of halide ion present, I have found it desirable to add additional water-soluble halide, particularly iodide, to the silver halide emulsion after its precipitation but before it is coated. More generally, about .1 to 50 mole percent, and preferably about 1 to 10 mole percent of water-soluble halide based on the silver halide in the emulsion are present in the subject emulsions. Illustrative water-soluble halides include the ammonium, calcium, lithium, magnesium, potassium, and sodium salts.

Lead ions can be used in the precipitation or formation of the silver halide used in the emulsions of the invention. Water-soluble lead salts are typically added with a water-soluble silver salt to an appropriate water-soluble halide to precipitate a lead-silver halide. The amount of lead used in the present silver halide emulsions typically ranges from about .01 to 5 mole percent based on the silver. The use of such lead ions in the formation of the silver halide facilitates the reduction of background density (D while exhibiting increased image density (D when exposed to a high intensity light source and photodeveloped by exposure to a lower intensity light source.

Halogen acceptors of the type utilized in conventional light-developable, direct-print silver halide emulsions can be incorporated in the present emulsions. Typical halogen acceptors that can be utilized in the emulsions of the invention include stannous chloride, thiosalicyclic acid, 1-phenyl-3-pyrazolidone, thiourea, thiosemicarbazide, 1- methyl 2-imidazolethione, l-n-butyl-l,2,5,6-tetrahydro- 1,3,5-triazine-4-thiol, D-mannose thiosemicarbazone, lphenyI-S-mercaptotetrazole, 4-thiobarbituric acid, urazole, 3-thiourazole, l-phenylurazole, 4-ethylurazole, 3- iminothiourazole and the like halogen acceptors.

A Wide variety of hydrophilic, water-permeable organic colloids can be suitably utilized in preparing the silver halide emulsions or dispersions of the invention. Gelatin is preferably utilized although other colloidal material such as colloidal albumin, cellulose derivatives, synthetic resins or the like can be utilized. Suitable colloids that can be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe, US. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 19 to 26% as described in US. Patent 2,327,808 of Lowe and Clark, issued Aug. 24, 1943} a Water-soluble ethanolamine cellulose acetate as described in Yutzy, US. Patent 2,322,085, issued June 15, 1943; a polyacrylamide having a combined acrylamide content of 30 to 60% and a specific-viscosity of 0.25 to 1.5 of an imidized polyacrylamide of like acrylamide content and viscosity as described in Lowe, Minsk and Kenyon, US. Patent 2,541,474, issued Feb. 13, 1951; zein as described in Lowe, US. Patent 2,563,791, is-suedAug. 7, 1951; a vinyl alcohol polymer containing urethane carboxylic acid groups of the type described in Unruh and Smith, US. Patent 2,768,154, issued Oct. 23, 1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in Unruh, Smith and Priest, US. Patent 2,808,331, issued Oct. 1, 1957; or a polymeric material which results from polymerizing a protein or a saturated acrylated protein with a monomer having a vinyl group as described in Illingsworth, Dann and Gates, US. Patent 2,852,382, issued Sept. 19, 1958.

The silver halide emulsions of my invention can be spectrally sensitized with cyanine and merocyanine dyes, such as those described in Brooker, US. Patents 1,846,- 301 (issued Feb. 23, 1932), 1,846,302 (issued Feb. 23, 1932), and 1,942,854 (issued Jan. 9, 1934); White, U.S. Patent 1,990,507 (issued Feb. 12, 1935); Brooker and White, US. Patents 2,112,140 (issued Mar. 22, 1938), 2,165,338 (issued July 11, 1939), 2,493,747 (issued Jan. 10, 1950), and 2,739,964 (issued Mar. 27, 1956); Brooker and Keyes, US. Patent 2,493,748 (issued Jan. 10, 1950); Sprague, US. Patents 2,503,776 (issued Apr. 11, 1950) and 2,519,001 (issued Aug. 15, 1950); Heseltine and Brooker, US. Patent 2,666,761 (issued Jan. 19, 1954); Heseltine, US. Patent 2,734,900 (issued Feb. 14, 1956); VanLare, US. Patent 2,739,149 (issued Mar. 20, 1956); and Kodak Limited British Patent 450,958, accepted July 15, 1936.

The silver halide emulsions of the invention can also contain any of the conventional addenda of light-developable, direct-print emulsions such as gelatin plasticizers, hardeners, coating aids and the like.

The above-described emulsions of the invention can be coated on a wide variety of supports in accordance with usual practice. Typical supports for photographic elements of the invention include glass, metals, paper, polyethylene-coated paper, polypropylene-coated paper, cellulose nitrate film, cellulose acetate film, polycarbonate film, polyvinyl acetal film, polystyrene film, polyethyleneterephthalate film and related films of resinous materials and others.

In forming a light-developed image with a typical photographic element containing an emulsion of the invention, the photographic element is initially exposed to a relatively short duration and high intensity source of electromagnetic radiation (e.g., at least about .1 footcandle second at an intensity of more than about 100 foot-candles) such as a high intensity light source such as are used in oscillographs described in Heiland, US. Patent 2,580,427, issued Jan. 1, 1952, high intensity visible light, x-radiation and the like, to form a latent image in the emulsion of the photographic element. Typical suitable high-intensity light sources are mercury vapor lamps that have high blue and ultraviolet emission, xenon lamps that emit light of wavelengths similar to daylight, and tungsten lamps that have high red light emission. Thereafter, the resulting latent image is photodeveloped by overall exposure of the emulsion to a radiation source (e.g., at least about .0001 foot-candle second) of lower intensity than the original exposure, such as to a conventional fluorescent light, light from incandescent lamps commonly used for general illumination, or even ordinary daylight. Generally, the latent image formed in the emulsion in the first instance is not visible and does not become visible until photodevelopment. Heat is desirably utilized during the photodevelopment step. Typically the subject emulsions are heated to a temperature of about 6 C. to 200 C. for about 1 to 30 seconds and photodeveloped after the initial high intensity exposure.

If desired, photographic elements containing the emulsions of the invention can be developed and fixed in aqueous chemical developing-out and fixing solutions after the initial exposure forming the latent image, or after the above-described photodevelopment, to make archivalquality records. Developing agents can be incorporated in the emulsions of the invention including such developing agents as hydroquinones, catechols, amino-phenols, 3-pyrazolidones and the like.

Photographic elements having the light-developable, direct-print silver halide emulsions coated thereon are particularly characterized in possessing a combination of properties desired of such materials, particularly, relatively high speed, resistance to image fading and good chemical development characteristics.

While photodeveloped visible images prepared with the present emulsions have high resistance to fading in ambient light, such images can be further inhibited from fading by coating thereover a filter material that absorbs light in the regions of the spectrum in which the emulsions are sensitive. Overcoated layers containing ultraviolet absorbing materials and dyes as 2,5-bis(2-decyloxy-x-sulfophenyl)thiazolo[5,4-di] thiazole disodium salt, 2,5-bis(Z-methyl-x-sulfophenyl)thiazolo[5,4 d]thiazole, Spirit Yellow I, Auramine G, Azobenzene, Auramine R, and the like are useful. Photodeveloped images can be conveniently overcoated with such filter materials by means of an aerosol spray comprising a fast drying dyed lacquer (eg, a cellulose lacquer) which does not transmit substantial light in the spectral region causing photochemical action in the underlyin silver halide emulsion. Also, photographic elements containing the emulsions of the invention can contain an overcoated mordant layer, and a photodeveloped image in such emulsions inhibited from fading 'by bathing the photographic image in a solution of a suitable mordantable dye such as C. 1. Acid Yellow 1, C, I. Acid Yellow 23, C. I. Direct Yellow 50, C. I. Acid Yellow 27, C. 1. Acid Yellow 17 and the like.

The present invention is further illustrated by the following examples of preferred embodiments thereof.

EXAMPLE 1 A series of light-developable, direct-print, light-sensitive gelatino silver chlorobromide (5 mole percent chloride and mole percent bromide) emulsions were prepared by slowly adding an aqueous solution of silver nitrate containing 0.85 g. of lead nitrate per mole of silver nitrate and a solution of potassium bromide and sodium chloride to an agitated 1.1% aqueous gelatin solution at 60 C. with the pH adjusted to about 2.0 with nitric acid. Various addenda were added to be present during the precipitation oft he silver halide in the preparation of the various emulsions as summarized below in Table A. The concentrations of the respective addenda are indicated in Table A in terms of grams per mole of silver halide,

TABLE A Emulsion: Addendum A 1,8-dihydroxy-3,6-dithiaoctane (2.6 grams) sodium thiocyanate (2.2 grams). B Sodium thiocyanate (2.2 grams). C Sodium thiocyanate (4.8 grams). D 1,8-dihydroxy-3,6-dithiaoctane (2.6 grams).

'E 1,8-dihydroxy-3,6-dithiaoctane (4.8 grams). F 1,8-dihydroxy-3,6-dithiaoctane (2.6 grams) sodium thiosulfate (2.2 grams).

An emulsi'm of the invention.

To each of the prepared emulsions was added about .4 mole percent based on the silver halide of a thiourea halogen acceptor, and about 2 mole percent based on the silver halide of potassium iodide. Each of the emulsions was also spectrally sensitized with a thiazoline-thiohydantoin merocyanine dye as described in copending Jones application Ser. No. 380,044 filed July 2, 1964. The emulsions were then coated on a photographic paper support at a silver coverage of 260 mg. per square foot and at a gelatin coverage of 480 mg. per square foot. The coatings were exposed through a 0.15 log E neutral density step wedge for 10 seconds in an EG&G Mark VI sensitometer. The resulting latent images in the coated emulsions were photo-developed with an overall exposure to daylight fluorescent illumination for minutes, 35 footcandles. Maximum and minimum density readings were observed as well as the number of visible 0.15 log E steps. The maximum densities (D are the densities in the areas of exposure and the minimum densities (D are the densities in background or nonimage areas, The number of visible 0.15 log E steps is an indication of the photographic speed of the respective emulsions. The resulting photodeveloped coatings were then subjected for 63 hours to 70 foot-candles of daylight fluorescent light and D D and number of 0.15 density steps observed to measure print permanence of the images. The results are summarized by the data set out in Table B below.

TAB LE B Image Discrimination After Photodevelopment (D =D min) Fluorescent Light 23 None. Minus 1 Step. D0. D 17 Do. E Do. F (No significant image discrimination on photodevelopment) The data set out in Table B illustrates that the use of a water-soluble thiocyanate in combination with an organic thioether silver halide solvent (Emulsion A, an emulsion of the invention) results in a light-developable, directprint silver halide emulsion having higher image discrimination and image permanence than do similar emulsions prepared with either of such addenda alone or with the silver halide solvent, sodium thiosulfate, utilized in preparing Emulsion F.

EXAMPLE 2 The photographic emulsions of the invention can also be chemically developed after imagewise exposure and photo-development if such is desired to make archival quality records. A photographic element having coated thereon Emulsion A described in Example 1 was exposed and photodeveloped as described in Example 1. The resulting photographic element was chemically developed in Kodak D-72 developer for 60 seconds at 70- F., and thereafter fixed in hypo, washed and dried in the usual manner. The original D areas of the photodeveloped emulsion did not chemically develop to a substantial density while the original D areas of the photodeveloped emulsion did chemically develop to a high density. A reversal image was obtained. An image discrimination (D D of 0.64 was obtained EXAMPLE 3 Similar results as those described in Examples 1 and 2 for Emulsion A are obtained if the silver halide of the light-developa'ble, direct-print silver halide emulsion of the invention is formed in the presence of 2.2 grams of potassium thiocyanate plus 2.0 grams of either 1,10- dithia-4,7,13,l6-tetraoxacyclooctadeoane, 4,10-dioXa-1,7- dithiacyclododccane, 1,17 di(N-ethylcarbamyl) 6,12- dithia-9-oxal1e ptadecane, 3,15-dioxa-6,9,IZ-trthiaheptadecane, 10,13 diaza3,20-dioxa-9,14-dioxo-6,17-dithi-adocosane, 3,6,9-trithiaundecane-1,1l-diol or 6,9-dioxa-3,l2-dithiatetradecane-1,14-diol, in lieu of the sodium thiocyanate plus the 1,8-dihydroxy-3,6-dithiaoctane used in preparing Emulsion A, concentrations being based on grams per mole of silver halide in the emulsion.

The present invention thus provides a new and useful class of light-developable, direct-print silver halide emulsions. Such emulsions are particularly characterized as possessing a combination of properties highly desirable in the present field, including high photodeveloped image discrimination, high print permanence, high sensitivity, and good chemical processing capability. The present emulsions have high sensitivity for both high speed and low speed recording.

The invention has been described in considerable detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be efiected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A light-developable, direct-print silver halide emulsion containing silver halide grains formed in an acid media in the presence of a water-soluble thiocyanate and and organic thioether silver halide solvent, an aqueous solution of said thioether at a 0.02 molar concentration being capable of dissolving more than twice the amount of silver chloride than that which can be dissolved by water at 60 C.

2. A light-developable, direct-print silver halide emulsion as described in claim 1 wherein lead ions were present during the formation of the silver halide grains.

3. A light-developable, direct-print silver halide emulsion as described in claim 1 wherein the water-soluble thiocyanate is selected from the group consisting of sodium thiocyanate and potassium thiocyanate.

4. A light-developable, direct-print silver halide emulsion as described in claim 1 wherein the organic thioether silver halide solvent has a formula selected from the group consisting of )s wherein R is an alkylene radical having 1 to 5 carbon atoms, R is an alkyl radical having 1 to 5 carbon atoms, R is an alkylene radical having 1 to 5 carbon atoms, r is an integer of 1 to 3 and s is an integer of 1 to 2.

A light-developable, direct-print silver halide emulsion as described in claim 1 wherein the silver halide is dispersed in gelatin.

6. A light-developable, direct-print silver halide emulsion as described in claim 1 wherein the thioether has the formula:

wherein r is an integer of 1 to 3.

7. A light-developable, direct-print silver halide emulsion as described in claim 1 wherein the thioether has the formula (CH2OH2O)..CH2CH2 s s (oHgoH20).oH2oH2 wherein s is an integer of 1 to 2.

8. A light-developable, direct-print silver halide emulsion as described in claim 1 wherein the said halide contains at least about 50 mole percent bromide.

9. A light-developable, direct-print silver halide emulsion as described in claim 1 wherein the water-soluble thiocyanate and the organic thioether silver halide solvent are each utilized during the formation of the silver halide grains at a concentration of about .1 to 50 grams per mole of silver halide.

10. A light-developable, direct-print gelatino silver halide emulsion wherein said halide contains at least about 50 mole percent bromide and wherein the silver halide grains are formed in the presence of:

(a) about .01 to 5 mole percent of a water-soluble lead salt based on said silver halide,

(b) about .1 to 50 grams of a water-soluble thiocyanate selected from the group consisting of sodium thiocyanate and potassium thiocyanate per mole of said silver halide, and

() about .1 to 50 grams of an organic thioether silver halide solvent selected from the group consisting of: 1,l0-dithia-4,7,13,16-tetraoxycyclooctadecane,

1,17 di(N ethylcarbamyl)-6,12-dithia-9-oxaheptadecane,

3,l-dioxa-6,9,IZ-trithiaheptadecane,

10,13 diaza 3,20 dioxa-9,14-dioxo 6,l7-dithiadocosane,

6,9-dioxa-3,IZ-dithiatetradecane-l,14-diol,

3,6,9-trithiaundecane-1,1 l-diol,

4,IO-dioxa-1,7-dithiacyclododecane, and

10 1,8-dihydroxy-3,6-dithiaoctane per mole of said silver halide.

11. A light-developable, direct-print silver halide emulsion as described in claim 1 wherein the organic thioether silver halide solvent contains at least one moiety wherein ether oxygen and sulfur atoms are separated by an ethylene radical.

12. In the process for preparing light-developable, direct-print silver halide emulsions, the improvement which comprises forming the grains of said silver halide in an acidic media in the presence of a water-soluble thiocyanate and an organic thioether silver halide solvent, an aqueous solution of said thioether at a 0.02 molar concentration being capable of dissolving more than twice the amount of silver chloride than that which can be dissolved by water at C.

References Cited UNITED STATES PATENTS 3,260,605 7/1966 Sutherns 96-107 X 3,271,157 9/1966 McBride 96-107 X NORMAN G. TORCHIN, Primary Examiner R. E. FICHTER, Assistant Examiner US. Cl. X.R. 96-107 

